I love coming across good deals on used computers.
Plus, there's nothing more flexible than having a spare laptop that still does 90% of what you need a computer for.
I bought a Thinkpad T21 the other week. 846MHz Pentium III, 256MB RAM, 35GB HDD, CD-RW drive for $40. Turns out it's the high-res 1400x1050 option for this model too, and it runs NetBSD great. I also got a $30 brand new battery and a $15 used PC100 memory upgrade coming in the mail.
So if I ever have to travel around or go someplace where it'd be risky but nice to have a laptop, I can grab this one and leave my Macbook safe and sound at home. And if I lose it, I'm only out $90 tops.
I also picked up a $120 Thinkpad T41 and installed Ubuntu Linux on it for my dad, so he has something to browse the Internet and watch movies with.